Use PHPStorm/WebStorm for git diff and merge tools

.gitconfig

# ~/.gitconfig
# Add this to your global git configuration file
# Change phpstorm to webstorm, if you use that.

# Diff and merge tool changes
# Run `git difftool <directory/file>...` or `git mergetool <directory/file>...`
[merge]
	tool = phpstorm
[diff]
	tool = phpstorm
[difftool]
; This setting is optional, but prevents an annoying prompt between diffing files.
	prompt = false
[difftool "phpstorm"]
; Putting this path here doesn't work. I would love to know why.
;	path = /Applications/PHPStorm.app/Contents/MacOS
	cmd = webide diff $(cd $(dirname "$LOCAL") && pwd)/$(basename "$LOCAL") $(cd $(dirname "$REMOTE") && pwd)/$(basename "$REMOTE")
	trustExitCode = true
[mergetool "phpstorm"]
	cmd = webide merge $(cd $(dirname "$LOCAL") && pwd)/$(basename "$LOCAL") $(cd $(dirname "$REMOTE") && pwd)/$(basename "$REMOTE") $(cd $(dirname "$BASE") && pwd)/$(basename "$BASE") $(cd $(dirname "$MERGED") && pwd)/$(basename "$MERGED")
	trustExitCode = true

.profile

# Add this to your .profile, .zshrc, .bashrc, etc.

# Add PHPStorm's bin directory to your path.
export PATH="/Applications/PHPStorm.app/Contents/MacOS:$PATH"

JetBrains support supplied this to fix it: https://confluence.jetbrains.com/display/PhpStorm/PhpStorm+Early+Access+Program

Verified working: PhpStorm-EAP-162.1447.5.dmg

None of the solution worked for me Webstorm 2016.2, unless I set
prompt = true
Then even the handy solution of JohnAlbin works.

If prompt = false, only the first file in the list is opened correctly, then all the other files are not found, prompting:
Error showing diff: Can't find file /tmp/Us1QSf_myfile.js

@thoma5B You just saved me some headaches with that prompt, thanks mate.

If you can not find wstorm, open WebStorm, and go to Tools in menu bar then click Command-line Laucher. My WebStorm version is 2016.2.3.

BTW, I can directly use the solution of @JohnAlbin. Thanks.

• You can also configure it with commands like git config --global mergetool.pstorm.trustExitCode true.
• You can use difftool --dir-diff, but currently tmp-files may be instantly removed, so I appended my difftool.pstorm.cmd with ; read and press Enter after diff completion.

FYI: @zored I had to use && read instead on my system, in order for it to not delete the files before I'm done with them.
But that way, it works (for me too). Great work around, though! 👍 😉

P.S.: adding an additional --symlinks flag to the difftool --dir-diff is also a nice "upgrade"...